CN115700938A

CN115700938A - Preparation method of metal lithium battery cathode

Info

Publication number: CN115700938A
Application number: CN202211478592.9A
Authority: CN
Inventors: 王思凡; 程可文; 唐本升; 伍淑滨; 王礼英
Original assignee: Hunan Juheyuan Technology Co ltd
Current assignee: Hunan Juheyuan Technology Co ltd
Priority date: 2022-11-23
Filing date: 2022-11-23
Publication date: 2023-02-07

Abstract

The invention discloses a preparation method of a metal lithium battery cathode, which comprises the following specific preparation steps: mixing an organic ligand which is 5-amino isophthalic acid and a metal ion center source which is copper nitrate into a mixed solution of N-N dimethylformamide and ethylene glycol, transferring the prepared solution into a reaction kettle, and carrying out hydrothermal synthesis to obtain a Cu-MOF material; adding a binder PVDF and a conductive agent Super-P into a Cu-MOF material to prepare an organic coating; and coating the prepared organic coating and the metal lithium sheet, and then placing the organic coating and the metal lithium sheet in a drying oven for drying to obtain the metal lithium electrode sheet. The lithium ion battery has good specific surface area and uniform and large pore size distribution, the precipitation space of metal lithium is enlarged, the distribution condition of lithium ions can be regulated, the formed frame structure can face the volume expansion of a lithium cathode, the occurrence of side reaction of the cathode is reduced, the cycle performance and the safety performance of a product are improved, and meanwhile, copper can further store lithium by alloying reaction with lithium.

Description

Preparation method of metal lithium battery cathode

Technical Field

The invention relates to the technical field of preparation of lithium battery electrode materials, in particular to a preparation method of a metal lithium battery cathode.

Background

Metallic lithium has high specific capacity and low electrochemical potential, and is an ideal high-energy-density negative electrode material. The solid-state battery using metallic lithium as the negative electrode is a new trend to replace the graphite negative electrode, but the lithium device cannot be commercially splendid due to the potential safety hazard caused by the dendrite effect of the metallic lithium. The so-called dendrite effect is the uncontrolled growth of lithium dendrites during cycling, and ideally, the metal will be deposited uniformly on the negative electrode, but in practice, the metal will be preferentially deposited where the tips of the negative electrode surface are raised, and when the lithium dendrites grow to a certain extent, they can penetrate the solid electrolyte, causing short circuit failure of the battery. In addition, "dead lithium" formed by the winding or breaking of lithium dendrites can cause a severe degradation of the battery capacity.

Metal Organic Frameworks (Metal Organic Frameworks) are a porous material that is formed by clustering Metal ions and Organic ligands. The material with MOF structure has the advantages of high porosity, large specific surface area, good thermal stability, ordered crystal structure and low density.

The current negative electrode lithium storage mechanism is: a negative electrode carbon material and TiO2 are embedded into a reaction mechanism; an alloying reaction mechanism of Si, se and Sn; a substitution reaction mechanism of transition metal oxide or sulfide. The embedding of the negative electrode carbon material is developed most widely, but the specific capacity of the negative electrode carbon material is not enough to meet the higher requirement and development of the negative electrode of the lithium battery, and the current alloying reaction mechanism is in a research hotspot.

Compared with a graphite negative electrode, although the lithium metal has higher specific capacity and cycle rate, the transformation of a phase change structure between lithium ions and the lithium metal is unstable in the cycle process, and the volume of the lithium metal changes to a certain extent. Secondly, the extremely high chemical activity of lithium metal causes an increase in side reactions, such as the formation of an SEI film on the surface. In addition, the instability of the phase structure and the change of the volume can reduce the gaps between materials or cause the extrusion and damage between materials, the extrusion between lithium and SEI films commonly causes SEI film fragmentation, the breakage/pulverization of lithium dendrites to form dead lithium or penetrate through a diaphragm to cause short circuit, and the mechanical damage in the solid electrolyte environment is more prominent.

Disclosure of Invention

The invention aims to solve the technical problem that the preparation method of the negative electrode of the metal lithium battery can effectively relieve the problems of unstable structure and dendritic crystal growth of the metal lithium in the prior art.

The invention is realized by the following technical scheme: a preparation method of a metal lithium battery cathode comprises the following specific preparation steps:

s1, mixing an organic ligand which is 5-amino isophthalic acid and a metal ion center source which is copper nitrate into a mixed solution of N-N dimethylformamide and ethylene glycol, and uniformly mixing and stirring to obtain a solution A;

s2, transferring the solution A prepared in the S1 to a stainless steel reaction kettle with a polytetrafluoroethylene lining for hydro-thermal synthesis, cooling the solution, and then cleaning and drying to obtain a Cu-MOF material;

s3, adding a binder PVDF and a conductive agent Super-P into the Cu-MOF material to prepare an organic coating;

and S4, coating the prepared organic coating and the metal lithium sheet, and drying in a drying oven at 55 ℃ for 3-4 hours to obtain the metal lithium electrode plate.

As a preferable technical scheme, the organic ligand used by the precursor solution prepared in the step S1 is 5-amino isophthalic acid, the metal ion center source is copper nitrate, and the rest reagents are N-N dimethylformamide, ethylene glycol and absolute ethyl alcohol.

As a preferable technical scheme, the organic ligand used by the precursor solution prepared in the step S1 is 5-amino isophthalic acid, the metal ion center source is copper nitrate, the mixture ratio of the materials is 70-80 parts and 20-30 parts, and the pH value of the solution is controlled to be 3-5.

As a preferable technical scheme, the reaction time of the Cu-MOF material prepared in the step S2 is 12-24 hours, and the reaction temperature is 100-150 ℃.

Preferably, the ratio of the binder and the conductive agent used in step S3 is 2% and 1.5%, respectively.

Preferably, the drying time of the Cu-MOF negative electrode material prepared in the step S4 is 3-4 hours, and the drying temperature is 50-75 ℃.

The beneficial effects of the invention are: the metal organic framework used in the invention has good specific surface area and uniform and larger pore size distribution, the precipitation space of metal lithium is enlarged, the distribution condition of lithium ions can be regulated and controlled, the formed framework structure can face the volume expansion of a lithium cathode, and the occurrence of side reaction of the cathode is reduced, so that the cycle performance and the safety performance of the product are improved, and simultaneously, copper can further store lithium by alloying reaction with lithium.

Detailed Description

All of the features disclosed in this specification, or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.

Example 1

The preparation method of the metal lithium battery cathode comprises the following steps:

step 1, measuring 0.5g of copper nitrate and 0.4g of 5-amino isophthalic acid in a mixed solution of 40ml of DMF and 25ml of EG, stirring at room temperature until the copper nitrate and the 5-amino isophthalic acid are completely fused, and controlling the pH value of the solution to be between 3 and 5 to serve as a pretreatment solution;

and 2, measuring 35ml of the pretreatment liquid obtained in the step 1, and putting the pretreatment liquid into a 50ml stainless steel reaction kettle with a polytetrafluoroethylene lining. The heating temperature is 80 ℃ and the reaction time is 12 hours respectively. After the reaction kettle is cooled to room temperature, washing the sample with DMF and absolute ethyl alcohol for many times respectively;

step 3, performing surface treatment on the metal lithium, soaking a 20-20 cm metal foil in absolute ethyl alcohol until the foil just submerges, and performing ultrasonic treatment for 5min;

and 4, adding 2% and 1.5% of adhesive and conductive agent by mass percent into the sample, fully mixing, and coating on a metal lithium sheet.

Step 5, the sample is then placed in a vacuum oven and dried at 50 ℃ to 75 ℃ for 3 hours. A metallic lithium negative electrode was obtained.

Example 2

step 1, weighing 0.5g of copper nitrate and 0.4g of 5-amino isophthalic acid, dissolving in 40ml of mixed solution of DMF and 25ml of EG, and stirring at room temperature until the copper nitrate and the 5-amino isophthalic acid are completely fused to obtain a pretreatment solution;

and 2, measuring 35ml of the pretreatment liquid obtained in the step 1, and putting the pretreatment liquid into a 50ml stainless steel reaction kettle with a polytetrafluoroethylene lining. The heating temperature is 80 ℃ and the reaction time is 12 hours respectively. After the reaction kettle is cooled to room temperature, washing the sample with DMF and absolute ethyl alcohol for multiple times respectively;

step 3, performing surface treatment on the metal lithium, soaking a 20-20 x-20cm metal foil in absolute ethyl alcohol until the foil just submerges, and performing ultrasonic treatment for 5min;

This example was conducted in the same manner as example 1 except that the pH of the solution was not controlled.

Example 3

step 1, measuring 0.5g of copper nitrate and 0.4g of 5-amino isophthalic acid, dissolving in a mixed solution of 40ml of DMF and 25ml of EG, stirring at room temperature until the mixture is completely fused, and controlling the pH value of the solution to be between 3 and 5 to serve as a pretreatment solution;

and 2, measuring 35ml of the pretreatment liquid obtained in the step 1, and putting the pretreatment liquid into a stainless steel reaction kettle with a 50ml polytetrafluoroethylene lining. The heating temperature is 80 ℃ and the reaction time is 12 hours respectively. After the reaction kettle is cooled to room temperature, washing the sample with DMF and absolute ethyl alcohol for many times respectively;

and 4, adding 2% and 1.5% of binding agent by mass percent into the sample, fully mixing, and coating on a metal lithium sheet.

This example is the same as example 1 except that no conductive agent is added.

Example 4

This example is similar to the first example except that the thickness of the coating is 20 μm and 25 μm, respectively.

The experimental results are as follows:

the battery assembly process is carried out according to a method well known in the art, and the used positive electrode is a lithium cobaltate positive electrode material. All test conditions were carried out at normal temperature and pressure (25 ℃).

The electrode plates of the first and third embodiments are respectively used as the negative electrode of the battery, the positive electrode adopts the same lithium cobaltate as the raw material, the manufacturing method of the positive electrode material is not detailed here, and as a comparison, the metal lithium plate without the metal organic framework coating is used as the control group. The experimental result is that under the condition of the current density of 2mAh/cm < 2 >, the electrode plate of the first example is 76 times of the cycle time of uncoated metallic lithium and is 8 times of metallic lithium without adding a conductive agent of the third example.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that are not thought of through the inventive work should be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope defined by the claims.

Claims

1. A preparation method of a metal lithium battery cathode is characterized by comprising the following specific preparation steps:

2. The method of manufacturing a negative electrode for a lithium metal battery according to claim 1, wherein: the organic ligand used by the precursor solution prepared in the step S1 is 5-amino isophthalic acid, the metal ion center source is cupric nitrate, and the rest reagents are N-N dimethylformamide, ethylene glycol and absolute ethyl alcohol.

3. The method of manufacturing a negative electrode for a lithium metal battery according to claim 1, wherein: the organic ligand used by the precursor solution prepared in the step S1 is 5-amino isophthalic acid, the metal ion center source is copper nitrate, the material proportion is 70-80 parts and 20-30 parts, and the pH value of the solution is controlled to be 3-5.

4. The method of manufacturing a negative electrode for a lithium metal battery according to claim 1, wherein: the reaction time of the Cu-MOF material prepared in the step S2 is 12-24 hours, and the reaction temperature is 100-150 ℃.

5. The method of manufacturing a negative electrode for a lithium metal battery according to claim 1, wherein: the adhesive and the conductive agent used in the step S3 account for 2 percent and 1.5 percent respectively.

6. The method of manufacturing a negative electrode for a lithium metal battery according to claim 1, wherein: the drying time of the Cu-MOF negative electrode material prepared in the step S4 is 3-4 hours, and the drying temperature is 50-75 ℃.